For instance, Patent Document 1 describes the following anti-theft system. A vehicle is equipped with an anti-theft device or an anti-theft component such as an immobilizer. For instance, the anti-theft device is for outputting an alarm by detecting a door opened and closed or the like by an unauthorized person. These anti-theft objects are periodically communicated with communications devices so that disassembling of these objects can be detected to thereby activate alarms. When the communications between the anti-theft objects and the communications devices becomes anomalous, it is determined that these anti-theft objects are stolen. The alarms are thereby outputted.                Patent Document 1: JP2003-137071 A        
The vehicle equipped with the above systems can detect using the anti-theft device a door opened and closed by an unauthorized person to thereby notify it, or prevent using the anti-theft component an unauthorized person from starting an engine. Further, disassembling or destroying the anti-theft objects can be detected to then activate an alarm, so that theft of the vehicle or the in-vehicle devices can be properly prevented.
However, even in the above vehicle, when the communications device or a device for outputting the alarm by detecting anomaly in the communications is disassembled or destroyed, the alarm cannot be outputted. This cannot securely prevent the theft of the vehicle. In particular, a malicious thief tries to steal a vehicle and cannibalize its components for selling to obtain an illegal profit. The cannibalized components can be used in other vehicles, so that the above-described countermeasure cannot eradicate such a theft.